This invention relates generally to packaging apparatus and more particularly to to form, fill and seal apparatus and methods for applying one way valves on packages formed from of tubular film stock using such apparatus.
Packaging large, e.g., approximately 50 pounds or 25 kilograms, of free flowing dry products in an appropriately sized bag and then stacking those filled bags onto a pallet for shipping has been done for many years. Historically the bag has been made from multiple layers of paper, plastic and sometimes aluminum foil. The bags seams have been closed by sewing or by gluing. When the bags are stacked onto a pallet, the air is allowed to escape the bag from the seams. This practice allows atmospheric moisture to enter the bag through the seams. Hygroscopic products such as nylon resin historically had issues with moisture gain when packaged by this method.
In the 1980's, pre-made heat sealed bags composed of moisture barrier laminates and fitted with one-way valves solved the problems with moisture gain seen on packages with sewn or glued seams. The seams of these bags do not allow air to escape and do not allow moisture to enter. The purpose of the one-way valve is to allow air to escape the bag when subjected to pressure from stacking bags on a pallet. Once the air pressure is relieved, the valve is closed and no moisture can enter the bag.
Recently rolls of plastic tubing have been utilized along with automatic fill and seal equipment to package free flowing dry products. The seams of these packages are leak free and the finished filled bags therefore need to be vented to allow air escape during palletization. Numerous methods have been used to vent these bags from simple punctures to elaborate tortuous paths. However, it has been determined that such vents are not as effective as desired inasmuch as they tend to allow moisture back into the package.
Therefore, there exists a need to improve the moisture barrier of the tube based bag due to moisture gain through the vents.
Further attempts have been made to remove air by displacement or vacuumization during the form and fill process, e.g., the form, fill and seal machines include a vacuum station for removing air from the interior of the package. However, the resulting packages are inconsistent in the amount of residual air left within the package, thereby resulting in poor palletization performance. In particular, when too much air is left, the bags on the lower pallet layers become pressurized making an unstable pallet load. When too much air is removed before palletization the bags hold the shape from filling and cannot flatten out to create a stable pallet load.
Thus, a need exists for apparatus configured to utilize a continuous tube of flexible material to form it into a series of flexible bag, to sequentially fill the bags, to apply a one-way valve to the bags, and to seal the bags, to provide bags which can be readily palletized. The subject invention addresses that need. To that end, the subject invention provides apparatus and method for producing packages, each including a one-way valve that allows air to escape from the package yet without allowing air to enter the package. Since those valves enable air to escape from each of the packages during palletization the packages can conform to one another creating a stable pallet load. Once air has escaped, the valve of each package closes and moisture cannot enter the package.